Fix M_ERRNO behavior on Windows

We use M_ERRNO flag in logging to display error code
and error message. This has been broken on Windows,
where we use error code from GetLastError() and
error description from strerror(). strerror() expects
C runtime error code, which is quite different from
last error code from WinAPI call. As a result, we got
incorrect error description.

The ultimate fix would be introducing another flag
for WinAPI errors, like M_WINERR and use either that or
M_ERRNO depends on context. However, the change would be
quite intrusive and in some cases it is hard to say which
one to use without looking into internals.

Instead we stick to M_ERRNO and in Windows case we
first try to obtain error code from GetLastError() and
if it returns ERROR_SUCCESS (which is 0), we assume that
we have C runtime error and use errno. To get error
description we use strerror_win32() with GetLastError()
and strerror() with errno.

strerror_win32() uses FormatMessage() internally, which
is the right way to get WinAPI error description.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20220503002840.295-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24270.html

Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/src/openvpn/error.c b/src/openvpn/error.c
index 603d6c6306817c5797dca493b622b0fa14d0c500..1b7f5cdec2cf025f21899b69438e5f0f5bd171b8 100644 (file)
--- a/src/openvpn/error.c
+++ b/src/openvpn/error.c
@@ -220,6 +220,18 @@ x_msg(const unsigned int flags, const char *format, ...)
     va_end(arglist);
 }
 
+static const char*
+openvpn_strerror(int err, bool crt_error, struct gc_arena *gc)
+{
+#ifdef _WIN32
+    if (!crt_error)
+    {
+        return strerror_win32(err, gc);
+    }
+#endif
+    return strerror(err);
+}
+
 void
 x_msg_va(const unsigned int flags, const char *format, va_list arglist)
 {
@@ -242,7 +254,8 @@ x_msg_va(const unsigned int flags, const char *format, va_list arglist)
         return;
     }
 
-    e = openvpn_errno();
+    bool crt_error = false;
+    e = openvpn_errno_maybe_crt(&crt_error);
 
     /*
      * Apply muting filter.
@@ -264,7 +277,7 @@ x_msg_va(const unsigned int flags, const char *format, va_list arglist)
     if ((flags & M_ERRNO) && e)
     {
         openvpn_snprintf(m2, ERR_BUF_SIZE, "%s: %s (errno=%d)",
-                         m1, strerror(e), e);
+                         m1, openvpn_strerror(e, crt_error, &gc), e);
         SWAP;
     }
 
@@ -643,7 +656,6 @@ x_check_status(int status,
                struct link_socket *sock,
                struct tuntap *tt)
 {
-    const int my_errno = openvpn_errno();
     const char *extended_msg = NULL;
 
     msg(x_cs_verbose_level, "%s %s returned %d",
@@ -666,26 +678,34 @@ x_check_status(int status,
                 sock->info.mtu_changed = true;
             }
         }
-#elif defined(_WIN32)
+#endif /* EXTENDED_SOCKET_ERROR_CAPABILITY */
+
+#ifdef _WIN32
         /* get possible driver error from TAP-Windows driver */
         if (tuntap_defined(tt))
         {
             extended_msg = tap_win_getinfo(tt, &gc);
         }
 #endif
-        if (!ignore_sys_error(my_errno))
+
+        bool crt_error = false;
+        int my_errno = openvpn_errno_maybe_crt(&crt_error);
+
+        if (!ignore_sys_error(my_errno, crt_error))
         {
             if (extended_msg)
             {
                 msg(x_cs_info_level, "%s %s [%s]: %s (fd=%d,code=%d)", description,
                     sock ? proto2ascii(sock->info.proto, sock->info.af, true) : "",
-                    extended_msg, strerror(my_errno), sock ? sock->sd : -1, my_errno);
+                    extended_msg, openvpn_strerror(my_errno, crt_error, &gc),
+                    sock ? sock->sd : -1, my_errno);
             }
             else
             {
                 msg(x_cs_info_level, "%s %s: %s (fd=%d,code=%d)", description,
                     sock ? proto2ascii(sock->info.proto, sock->info.af, true) : "",
-                    strerror(my_errno), sock ? sock->sd : -1, my_errno);
+                    openvpn_strerror(my_errno, crt_error, &gc),
+                    sock ? sock->sd : -1, my_errno);
             }
 
             if (x_cs_err_delay_ms)

diff --git a/src/openvpn/error.h b/src/openvpn/error.h
index ad7defe80e96152b1c50359564c07e6e65194cee..be8d97e50bfe7a3e931b8a092de71c6485226524 100644 (file)
--- a/src/openvpn/error.h
+++ b/src/openvpn/error.h
@@ -75,13 +75,10 @@ struct gc_arena;
 /* String and Error functions */
 
 #ifdef _WIN32
-#define openvpn_errno()             GetLastError()
-#define openvpn_strerror(e, gc)     strerror_win32(e, gc)
+#define openvpn_errno() GetLastError()
 const char *strerror_win32(DWORD errnum, struct gc_arena *gc);
-
 #else
-#define openvpn_errno()             errno
-#define openvpn_strerror(x, gc)     strerror(x)
+#define openvpn_errno() errno
 #endif
 
 /*
@@ -352,20 +349,22 @@ msg_get_virtual_output(void)
  * which can be safely ignored.
  */
 static inline bool
-ignore_sys_error(const int err)
+ignore_sys_error(const int err, bool crt_error)
 {
-    /* I/O operation pending */
 #ifdef _WIN32
-    if (err == WSAEWOULDBLOCK || err == WSAEINVAL)
+    if (!crt_error && ((err == WSAEWOULDBLOCK || err == WSAEINVAL)))
     {
         return true;
     }
 #else
-    if (err == EAGAIN)
+    crt_error = true;
+#endif
+
+    /* I/O operation pending */
+    if (crt_error && (err == EAGAIN))
     {
         return true;
     }
-#endif
 
 #if 0 /* if enabled, suppress ENOBUFS errors */
 #ifdef ENOBUFS
@@ -387,6 +386,26 @@ nonfatal(const unsigned int err)
     return err & M_FATAL ? (err ^ M_FATAL) | M_NONFATAL : err;
 }
 
+static inline int
+openvpn_errno_maybe_crt(bool *crt_error)
+{
+    int err = 0;
+    *crt_error = false;
+#ifdef _WIN32
+    err = GetLastError();
+    if (err == ERROR_SUCCESS)
+    {
+        /* error is likely C runtime */
+        *crt_error = true;
+        err = errno;
+    }
+#else
+    *crt_error = true;
+    err = errno;
+#endif
+    return err;
+}
+
 #include "errlevel.h"
 
 #endif /* ifndef ERROR_H */

diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c
index 8930e578a984be4828ce5017bb63f3a7dbe91308..04828a5c44ae9e05e1e8167361370aa99af33f9f 100644 (file)
--- a/src/openvpn/forward.c
+++ b/src/openvpn/forward.c
@@ -1660,7 +1660,14 @@ process_outgoing_link(struct context *c)
         }
 
         /* for unreachable network and "connecting" state switch to the next host */
-        if (size < 0 && ENETUNREACH == error_code && c->c2.tls_multi
+
+        bool unreachable = error_code ==
+#ifdef _WIN32
+            WSAENETUNREACH;
+#else
+            ENETUNREACH;
+#endif
+        if (size < 0 && unreachable && c->c2.tls_multi
             && !tls_initial_packet_received(c->c2.tls_multi) && c->options.mode == MODE_POINT_TO_POINT)
         {
             msg(M_INFO, "Network unreachable, restarting");

diff --git a/src/openvpn/manage.c b/src/openvpn/manage.c
index e305e44221a99288e3b078fc6fe69bfc93ee27f9..aeea5f9ff3ac1e37a09e3579c6707674808ef6d8 100644 (file)
--- a/src/openvpn/manage.c
+++ b/src/openvpn/manage.c
@@ -2008,9 +2008,10 @@ man_process_command(struct management *man, const char *line)
 static bool
 man_io_error(struct management *man, const char *prefix)
 {
-    const int err = openvpn_errno();
+    bool crt_error = false;
+    int err = openvpn_errno_maybe_crt(&crt_error);
 
-    if (!ignore_sys_error(err))
+    if (!ignore_sys_error(err, crt_error))
     {
         struct gc_arena gc = gc_new();
         msg(D_MANAGEMENT, "MANAGEMENT: TCP %s error: %s", prefix,

diff --git a/src/openvpn/platform.c b/src/openvpn/platform.c
index 61afee83ca6947caefee4981f98a6601aec37e64..ae1678dba10df179f73d46c30b68600523e8efc0 100644 (file)
--- a/src/openvpn/platform.c
+++ b/src/openvpn/platform.c
@@ -532,7 +532,7 @@ platform_test_file(const char *filename)
         }
         else
         {
-            if (openvpn_errno() == EACCES)
+            if (errno == EACCES)
             {
                 msg( M_WARN | M_ERRNO, "Could not access file '%s'", filename);
             }

diff --git a/src/openvpn/tun.h b/src/openvpn/tun.h
index 3a7314c52dde8c77c04812884fdf1e495cb12d00..4bc35916557713a32c9b615317ee9e8b66f5cc7b 100644 (file)
--- a/src/openvpn/tun.h
+++ b/src/openvpn/tun.h
@@ -446,7 +446,7 @@ tuntap_stop(int status)
      */
     if (status < 0)
     {
-        return openvpn_errno() == ERROR_FILE_NOT_FOUND;
+        return GetLastError() == ERROR_FILE_NOT_FOUND;
     }
     return false;
 }
@@ -459,7 +459,7 @@ tuntap_abort(int status)
      */
     if (status < 0)
     {
-        return openvpn_errno() == ERROR_OPERATION_ABORTED;
+        return GetLastError() == ERROR_OPERATION_ABORTED;
     }
     return false;
 }